Computer simulation of charging the silicon dioxide surface and subsurface layers by electron bombardment

A physical model and program of calculating the parameters of charging dielectrics by electron bombardment is described. A method of computer simulation is used to investigate the main processes of charging the subsurface silicon dioxide layers. Dependences of the current density, volume charge density, and electric field strength on the material layer depth are calculated for variable electron beam parameters, irradiation time, and grid potential near the sample surface.     

Features of the surface layers of TiNi-based alloy thin ribbons

The chemical composition of the surface of TiNi-based alloys in the form of ribbons produced by rapid melt quenching in oxygen-containing environment has been investigated. It is shown that titanium oxide is formed on the Ti₅₀Ni₂₅Cu₂₅ alloy surface, while on the Ti_39.2Ni_24.8Cu₂₅Hf₁₁ alloy surface titanium and hafnium oxides are formed. Atomic-force microscope images reveal crystalline structures of titanium oxide with sizes of up to 500 × 500 nm² on the surface of the Ti₅₀Ni₂₅Cu₂₅ sample. After removing the surface oxide layer by ion etching, the ratio of elements becomes close to the stoichiometric composition.     

Structure in surface frictional layers on 36NKhTYu alloy

A study has been made on how heat treatment affects surface-layer formation and structure in unlubricated friction on steel 45 for high-tensile austenitic 36NKh-TYu alloy. The substructure formed in the friction zone has multiple continuous and discrete orientation deviations and is independent of the initial alloy state. However, the aged alloy differs from the quenched in that there is turbulence in the surface-layer structure.Translated from Izvestiya Vysshikh Uchebnykh Zavedenii, Fizika, No. 8, pp. 9–12, August, 1991.We are indebted to Yu. V. Svitich for a discussion.     

Formation of metal and alloy surface layers at electroexplosive alloying

The structure-phase peculiarities of the surface layers, formed at electroexplosive alloying of steels and alloys with Al, Cu, B + Cu, C, and C + B have been studied by metallography and scanning and transmission electron microscopy. The treatment involving melt overheating under plasma jet pressure and subsequent cooling at a high rate is established to form nanosized phases. It is shown that different forms of electroexplosive treatment lead to the simultaneous increase in the microhardness, wear resistance, and heat resistance of the steel and alloy surface.     

应力导致InAs/In0.15Ga0.85As量子点结构中 In0.15Ga0.85As阱层的合金分解效应研究

利用固源分子束外延技术,在In0.15Ga0.85As/GaAs量子阱生长了两个InAs/In0.15Ga0.85As量子点(DWELL)样品.通过改变其中一个InAs DWELL样品中的In0.15Ga0.85As阱层的厚度和生长温度,获得了量子点尺寸增大而且尺寸分布更均匀的结果.结合光致发光光谱(PL)和压电调制光谱(PzR)实验结果,发现该样品量子点的光学性质也同时得到了极大的优化.基于有效质量近似的数值计算结果表明:量子点后生长过程中应力导致In0.15Ga0.85As阱层合金分解机理是导致量子点尺寸和光学性质得到优化的主要原因.     

Ordering kinetics in the alloy Au4Cr

The kinetics of the appearance of long-range order and the growth of antiphase domains (APD) in the alloy Au₄Cr with the superstructure Dl_a in the ordered state are studied by x-ray diffraction methods. The features of the incubation period are investigated. It is established that ordering in the alloy Au₄Cr occurs heterogeneously with the nucleation of well-ordered particles.Translated from Izvestiya Vysshikh Uchebnykh Zavedenii, Fizika, No. 12, pp. 98–105, December, 1991.     

The effect of femtosecond laser micromachining on the surface characteristics and subsurface microstructure of amorphous FeCuNbSiB alloy

Detailed studies on the effects of femtosecond laser ablation on surface characteristics and subsurface microstructure of amorphous FeCuNbSiB alloy are reported. Three types of ripple structures were observed on the material surface in the gentle ablated (damaged) zone. As observed with X-ray diffraction (XRD), amorphous form is kept in the damaged zone, and there is few crystallization form in ablation zone.     

Two-component model for the growth of porous subsurface layers

This paper studies a kinetic model that describes the interaction of two fluctuating densities. The model makes it possible to stably reproduce the growth of dense, porous, and fractal structures near the surface of solids placed in an active medium. The solutions of local and nonlocal equations of the model are studied, and the results are used to comment on the possible scenarios of the evolution of systems whose behavior can be reduced to such a model. Finally, the exponents of the growth of the front width in a steady-state regime are calculated for various values of the parameters. Zh. éksp. Teor. Fiz. 114, 1500–1515 (October 1998)     

Fundamentals of surface thermodynamics

The nonequilibrium behavior for mixtures of fluids in interfaces is discussed. In particular, a thermodynamic field theory is given for media in thin, curved regions (interfaces with finite thickness), which separates two media with different physical properties. The moving interface is considered as semipermeable and a generalized transport equation and specific balance equations are derived. A systematic investigation of constitutive equations is made and in the limit as the thickness of the interface goes to zero it is shown that all relevant interfacial relations can be found.     

Surface waves and surface thermodynamics

The surface analogue of the Debye model is used to study several questions of surface thermodynamics in different temperature ranges from a practical point of view. The model is about as useful as some rather more elaborate lattice dynamical calculations. Further thermodynamical analysis and appeal to some experimental data demonstrate important distinct features, characteristic of the case of solid surfaces, which cannot even approximately be described by these models. This establishes their practical limitation and emphasizes the role of a detailed atomistic picture. Incidentally, a theoretical misconception concerning the surface specific heat of Rayleigh waves is clarified by means of a detailed analysis of the different contributions to the surface density of modes.     

Statistical thermodynamics of the liquid surface

The current theoretical situation regarding the structure of the liquid-vapour transition zone and the associated thermodynamic surface properties of simple liquids is reviewed. The thermodynamic and statistical mechanical treatments of the surface structure are assessed, and it is concluded that the former approach has limiting validity only as T→T _crit. Liquid metal systems are discussed, together with the recent experimental evidence supporting the existence of stable density oscillations at the surfaces of certain liquid metals. The liquid inert gas systems, argon in particular, are considered in some detail, and a discussion of the statistical thermodynamics of the liquid ⁴He surface is given.     

Calculation of electron spectra and some problems in the thermodynamics of graphene layers

The expressions for the energy spectra of monolayer, bilayer, and multilayer graphene, as well as epitaxial graphene, are derived using the quantum Green’s functions method. Analytic expressions are obtained for the densities of states of these systems. It is shown that a bandgap can appear the spectrum of an epitaxial graphene bilayer. A number of problems in the thermodynamics of electrons in free and epitaxial graphene layers are considered as applications. Analytic expressions are obtained for the chemical potential and heat capacity in the limiting cases of low and high temperatures. Quantum oscillations of heat capacity in graphene are analyzed taking into account the Coulomb interaction. The Berry phase of epitaxial graphene is investigated.     

面心立方(001)方向AB合金薄膜表面层的有序无序相变

采用平均场近似方法对两组元面心立方合金薄膜的有序无序相转变过程进行模拟计算,结果表明,合金薄膜的有序无序相变受薄膜层数奇偶性的影响.薄膜层数奇偶性不同,会导致薄膜具有不同的相结构和热力学性质.在弱表面偏析作用下,对于偶数层薄膜,由于薄膜边界对称性破缺,对应体组分x=0.5的化学势区间,偶数层薄膜有序无序相变过程中出现了中间温度相和浸润现象.而奇数层薄膜的有序无序相变类似体材料的相变.在强表面偏析作用下,由于受表面偏析作用和有限尺寸效应影响,对应体组分x=0.5的化学势区间,奇数层薄膜中出现AB(AB)nA相,它不存在严格热力学意义上的有序无序相变.     

On the density of surface acoustic waves and surface thermodynamics in a piezoelectric

Piezoelectricity introduces new modes and modifies part of the elastic vibrational spectrum for both bulk and surface waves. This has a direct bearance on surface thermodynamics. A simple phenomenological model is studied analytically and exactly. This bears out the basic physics involved and allows for a quick and easy estimate of the changes to be expected, which turn out to be substantial.     

Generation of shear bands in subsurface layers of metals in sliding

Nanostructuring of the surface of specimens during friction is investigated under the conditions of shear instability of the subsurface layers of the material due to the strong localization of deformation. It is demonstrated that the localization of deformation in the subsurface layers occurs in three stages. The structure of the localization zone is studied. The formation of a nanocrystalline material on the surface due to the shear instability is considered by analogy with the formation of the shear band. The formation of the nanocrystalline material can be responsible for the crossover from the mild wear to the adhesive wear in the absence of mechanisms providing structural adaptability.     

Mg-Sn-Si系合金的热力学基础及合金相演变过程分析

研究了Mg-Sn-Si系合金的热力学基础及合金相的演变过程. 结果表明: 对于Mg-Sn-Si系合金, 合金相的比热容随着温度增加而增加, 在低温下变化迅速, 而在高温下变化平缓, 其热膨胀系数在低温范围内随温度升高呈指数形式增加, 而在高温范围内呈线性增大. 在Mg₂ (Si_x, Sn_1-x)、Mg₂ (Sn_x, Si_1-x)相结构中, Sn(Si)原子的取代位置不固定, 可以是面心, 也可以是顶点. 常规凝固过程中, 由于处于非平衡状态, x的取值范围有所波动, 对于Mg₂ (Si_x, Sn_1-x)和Mg₂ (Sn_x, Si_1-x) 两种结构, x的取值范围在0.25或0.75附近. Mg₂ (Si, Sn)的生成温度较高, 可从液相中直接析出, 也可由Mg₂Si转化而来, 而Mg₂ (Sn, Si)的生成温度较低, 只能从基体中析出, 随着Sn含量的增加, 开始析出Mg₂ (Sn, Si)相的温度升高.